True to the name, we use acid to remove the top layer of the plaster in the pool. The fresh plaster underneath the discolored plaster is of one color, and will give the pool a clean look. (Do not worry, pools always have at least 1/2” of excess plaster, so the acid wash will not break the pool plaster.) The general ratio of acid to water is 50/50. We first drain the pool of all its water to get to the plaster. After mixing the acid into the water (we mix the acid into the water always to prevent the container from melting) we pour the mixture around the edges of the pool. We use a brush to scrape off a very small layer of plaster, revealing the clean plaster underneath.